Cell Division Why do cells need to divide

Cell Division

Why do cells need to divide? • Living things grow by producing more cells, NOT because cells get bigger • If cells grew bigger, they could not get enough nutrients into the cell and wastes out of the cell. • Repair damaged tissue

Parent and Daughter • The original cell is called the parent cell • 2 new cells are called daughter cells • Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell • Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell

Daughter Cells Parent Cell

Cell Cycle • The cell cycle is the life cycle of a cell. • Begins when a cell is formed • Ends when the cell divides and forms new cells

3 Stages of Eukaryotic Cell Cycle Interphase Mitosis (PMAT) Cytokinesis When cells become old or damaged, they die and are replaced with new cells

Stage 1: Interphase • DNA replication (copying) occurs. • The cell also grows, carries out normal cell activities, replicates all other organelles. • The cell spends most of its life cycle in Interphase.

Stage 2: Mitosis (nuclear division) • division of the nucleus into 2 nuclei, each with the same number of chromosomes • Mitosis occurs in all the somatic (body) cells

Chromosome Number • Every organism has its own specific number of chromosomes • Examples: Human = 46 chromosomes or 23 pairs Dog = 78 chromosomes or 39 pairs Goldfish = 94 chromosomes or 47 pairs Lettuce = 18 chromosomes or 9 pairs

• All somatic (body) cells in an organism have the same kind and number of chromosomes • Example: Human = 46 chromosomes Human skin cell = 46 chromosomes Human heart cell = 46 chromosomes Human muscle cell = 46 chromosomes